1. Field of the Invention
The present invention relates to a display control technique of data broadcast content in which characters, image, voice, video are multiplexed.
2. Description of the Related Art
As digital satellite broadcasting service has started, data-broadcasting service is received by not only personal computers but also television receivers. With the television receiver having a receiving function of receiving data broadcast data and a replay software program (a data broadcast browser), even a user who has no personal computer views a variety of pieces of information and displays texts and images, associated with a television program, on the screen of the television receiver. Standards controlling such a service is Standard ARIB-STD-B24 formulated by the Association of Radio Industries and Business (ARIB) in Japan.
TV stations encodes ordinary TV program data, audio data, and data broadcasting data. After being multiplexed, these pieces of data are modulated and then transmitted from an antenna. A signal transmitted from the antenna is then delivered to a user terminal (a television receiver) through a broadcasting satellite (BS).
FIG. 17 is a block diagram showing the construction of a typical receiver for receiving typical digital satellite broadcast signals. The Standard of the ARIB permits the resolution of a video plane 107, still image plane 108, and character and drawing image plane 109 to be different from receiver to receiver. For example, the still image plane 108 may have two types of resolutions, namely, a resolution of 1920 pixels (horizontally) by 1080 lines (vertically), and a resolution of 720 pixels (horizontally) by 480 lines (vertically). With the still image plane 108 of a resolution of 720×480, an aspect ratio of width frame to height frame may be 16:9 or 4:3 on a display.
With the still image plane 108 of a resolution of 1920×1080, each pixel on the still image plane 108 is displayed as a square. But with a resolution of 720×480, each pixel of the still image plane 108 has a slightly horizontally elongated rectangular shape if the aspect ratio of the display is 16:9, and has a slightly vertically elongated rectangular shape if the aspect ratio of the display is 4:3. The display is available in a variety of sizes, for example, 14 inches, 19 inches, and 33 inches.
Digital data is repeatedly transmitted from TV stations in the data carousel method standardized in ISO/IEC13818-6. Digital data, filtered by a transport decoder, contains text information, script information, image information, and video and audio data. Text information is described using XML (extensible Markup Language) regulated by the Worldwide Web Consortium (W3C).
Attempts to provide services such as electronic shopping using data broadcasting have been made. For example, when a television-shopping program is in progress, detailed information about goods is delivered using data broadcasting. A user operates the television receiver to monitor the detailed information about a commercial product currently being introduced during the program.
In the electronic shopping using the television receiver, the size of the displayed image of each commodity becomes different depending on the size of a TV screen in use and the resolution of the TV. The real size of each commodity and the size of the commodity which users feel according to the displayed image fail to match each other.
Japanese Laid-Open Patent No. 9-006944 discloses an electronic catalog system to reproduce the size of the commodity. According to the disclosure, the electronic catalog system scales the image of a product in accordance with the size of a display screen to present the image of the product in the real size thereof.
As described above, however, the receiving environment such as the resolution of the still image plane 108 of the TV receiver, the size of the display, and the aspect ratio of the display screen during presentation may be different from user to user.
The technique, disclosed in the above-cited Japanese Laid-Open Patent No. 9-006944, simply performs a scaling process taking into consideration the screen size only. The aspect ratio of an original product may change depending on the specifications of a TV receiver of a user. This technique is unable to present a product in its real size, and thus it is difficult to cause the impression of the product on the TV display screen to the user to match the actual impression of the product.
In accordance with the cited disclosure, the user needs to input data of the screen size, and the image data of the product in the real size thereof is generated from particular image data. Depending on a combination of the size of a product, display screen size, and resolution, the image quality of the image of the product is substantially degraded during real-size presentation. On-screen realism of the product is thus damaged.
For example, if a product as large as 1 meter high is displayed on a 14-inch TV monitor in the real size thereof as shown in FIG. 18A, a portion of the product is conventionally displayed in enlargement. The image quality is thus degraded.
In the example shown in FIGS. 18A and 18B, the image of a “bicycle” as long as 1.5 m is presented in the real size thereof on a 14-inch size TV screen. A portion of the image shown in FIG. 18A is thus presented as shown in FIG. 18B. If the resolution of the image shown in FIG. 18A is not high enough, image quality substantially decreases as shown in FIG. 18B. Realism of the bicycle is lost.